This invention relates to a yarn feeder for use with a tufting machine.
Such a yarn feeder typically includes feed rolls for supplying pile yarns at predetermined speeds to respective needles of the tufting machine, which are aligned in the width direction of a fabric which is being fed through the tufting machine and on which pile yarns are to be stitched. By individually controlling the feed rates of the yarns, the lengths of piles formed by the respective pile yarns can be changed individually, so that tufted carpets having different pile patterns can be produced.
Such yarn feeders are disclosed in various prior art documents. For example, JP patent publication 61-19856 (unexamined) discloses a yarn feeder in which the feed rate of each pile yarn is controlled by changing the rotational speed of the corresponding feed roll in a plurality of stages. In order to change the rotational speed of the corresponding feed roll in a plurality of stages, a transmission must be provided between the respective feed roll and its drive unit.
The yarn feeder disclosed in JP patent publication 2-466 (examined) includes a plurality of roller sets. Each set comprises a plurality of feed rolls that are rotating at different speeds from each other, and idle rolls each opposing one of the feed rolls. Each pile yarn is passed between the feed rolls and idle rolls of one roller set. By selectively pressing only one of the idle rolls against the corresponding feed roll, the pile yarn can be fed at a speed corresponding to the rotating speed of any desired one of the feed rolls. In order to rotate the plurality of feed rolls at different speeds, they have to be individually driven by separate drive units. That is, it is necessary to provide as many drive units as the feed rolls.
For the above reasons, the yarn feeders disclosed in these prior publications are complicated in structure and expensive.
The yarn feeder disclosed in JP utility model publication 1-43424 includes a plurality of plate members elongated in the direction in which the needles of the tufting machine are aligned and formed with a plurality of holes in which are passed respective pile yarns. By moving the plate members in the direction perpendicular to the direction in which the needles are aligned, it is possible to change the feed lengths and thus the feed rates of the respective pile yarns. Compared to the yarn feeders disclosed in the first two publications, this yarn feeder is less complicated in structure. But in order to change the feed rate of each pile yarn to a meaningful extent, the plate members have to be moved or swung a rather long distance in the direction perpendicular to the direction in which the needles are aligned. This of course requires a large space in which the plate members can swing, which in turn increases the size of the yarn feeder and thus the entire tufting machine. Moreover, pile yarns passed through holes formed in any particular plate member cannot be pulled out of this particular plate member and inserted into another plate member while the tufting machine is in operation. This limits variation of pile patterns that can be formed on each tufted carpet, compared to variation of pile patterns that can be produced by the yarn feeders disclosed in the first two publications.
An object of the invention is to provide a yarn feeder for a tufting machine which is compact and simple in structure and is still capable of freely changing the heights of piles formed by each pile yarn on a fabric.